Biology -5.1.1 - Communciation and Homoestasis

Why do multicellular organisms need communication systems?

* To respond when their internal and external environment changes
* To coordinate organ function

What is cell signaling?

Communication between cells: Electrical signals carried by neurons or chemical signals as hormones

* Long distance endocrine signalling
* Paracrine signaling between adjacent cells occurs directly or aided by extracellular fluid
* Autocrine signalling cells release signals to stimulate it's own receptors and triggers a response within itself

What is homeostasis?

Internal environment is maintained with set limits around an optimum

What is negative feedback?

Self-regulatory mechanisms return internal environment to optimum when there is fluctuation

What is positive feedback?

A fluctuation triggers change that results in an even greater deviation from the normal level

What are receptors?

Specialised cells located in a sense organ that detect a specific stimulus

What are effectors?

Usually muscles or glands which enable a physical response to a stimulus

What is an ecotherm?

An organism that cannot increase its respiration rate to increase the internal production of heat.

It relies on external sources took regulates its body temperature and responds to temperature changes behaviourally , May orient body took minimise/maximise sun exposure

What is an endotherm?

Organism that can regulate its body temperature independently of external sources. Thermoreceptors send signals to the hypothalamus, which triggers a physiological or behavioral response

What behavioural methods do endotherms use top regulate their body temperature?

* Basking in the sun
* Pressing against warm surfaces
* Digging burrows
* Hibernation
* Panting (Heart lost as water evaporates from mouth)

How does the autonomic nervous system enable endotherms to thermoregulate?

Negative feedback - peripheral thermoreceptors detect changes in skin temperature and thermoreceptors in the hypothalamus detect changes in the blood temperature.

The hypothalamus sends impulses to effectors in skin(vasodilation/constriction) and muscles (shivering)

What is the role of the skin in thermoregulation?

Vasodilation/constriction of arteriosclerosis supplying skin capillaries controls heat loss to skin surface.

Hair erector muscles contract and follicles protrude to tap air for insulation

Evaporation of sweat cools skin surface